This invention concerns friction materials for lubricated tribological systems and particularly but not exclusively, for the manufacturing of synchro rings used in manual gear boxes.
The materials for gear boxes are subjected to several requirements, some of them contradictory. On the one hand, it is required to have an efficient lubrication at the gears, that is, a friction coefficient as low as possible between contact surfaces. On the other hand, at the synchros a friction coefficient as high as possible is required as well as a friction coefficient which is constant, independant particularly from temperature, sliding speed and contact pressure.
In synchros it is preferable to avoid oil films or to break them by creating geometrical irregularities by machined grooves, or fine irregularities by using a non-homogeneous material. However, these friction materials have produced variable results according to the functional conditions.